Spectroscopic ellipsometers are known for their capability to irradiate light onto a sample and then measure the polarization state of reflected light so as to calculate the film thickness and the optical constant of each layer. Especially in the case of film stacks composed of semiconductor or the like, such a spectroscopic ellipsometer is used for irradiating light and thereby calculating the film thickness and the optical constant (see, for example, Japanese Patent Application Laid-Open No. 2004-286468).
Nevertheless, conventional measuring apparatuses including that described in Japanese Patent Application Laid-Open No. 2004-286468 have a problem that a large amount of time and effort are necessary in the measurement for such characterization. Further, in the apparatus described in Japanese Patent Application Laid-Open No. 2004-286468, complicated processing and condition setting are necessary to perform calculation of the film thickness and the optical constant of a multilayer film stack such as an ONO (Oxide Nitride Oxide). Thus, it is difficult to measure efficiently an ONO film stack distributed over a large area on a wafer.